A scanning-type projection device, which projects vehicle information on a windshield, has been developed such that the vehicle information is displayed on the front side of the windshield of the vehicle in order to enable a driver of the vehicle to read the vehicle information (display image), such as a speed, without moving eyes during driving.
PTL 1 discloses a head up display device in which a scanning-type projection device uses a semiconductor laser as a light source for projecting a display image. The head up display device includes the semiconductor laser, a scanning system and a screen, scans a laser light, which is emitted from the semiconductor laser, toward the screen, and generates the display image.
In the head up display device, in which the laser light is used as the light source, the visibility of the display image is deteriorated due to spectrum based on the laser light. PTL 2 discloses a head up display device which reduces spectrum due to the laser light. In the head up display device disclosed in PTL 2, microlens arrays, which are arranged double, are used. Since the microlens arrays, which are arranged double, diverge the laser light according to a refraction operation performed by a microlens regardless of a diffusing agent and surface unevenness, it is possible to reduce the generation of the spectrum.
In addition, in the head up display, in which the laser light is used as the light source, it is difficult to perform stable display due to the threshold characteristic of the laser light source when an image, in which luminance is low, is displayed. Here, PTL 3 discloses a head up display in which it is possible to stably display an image, in which luminance is low, by arranging a polarization control element and a polarization unit, which causes a laser light having a specific polarization component to pass, on the optical paths of the laser light.